Avalanche photodiodes (APDs) are highly sensitive optical detectors. Avalanche photodiodes are reverse biased solid state devices. When a photon is absorbed in the device, an electron-hole pair is created. The mobile charge carriers accelerate through the semiconductor material due to the high electric field in the junction, generating more carriers via impact ionization. These secondary carriers also accelerate and impact-ionize, generating even more carriers, resulting in an avalanche. This process is called avalanche multiplication, and such devices can operate either with linear gain such that the average number of electrons generated is proportional to the average number of photons receiver, or when biased above a critical voltage, may enter a breakdown state in which the very large number of electrons generated is unrelated to the number of photons received. This invention pertains to APDs designed for linear mode operation.